1. Field of the Invention
The present invention relates to an endoscope including a bending portion, a bending radius of which can be changed, on a distal end side of an insertion portion.
2. Description of the Related Art
In recent years, endoscopes have widely been used in a medical field and an industrial field. In the case of endoscopes used in the medical field, e.g., an inside of a body can be observed by inserting an insertion portion into the body. Endoscopes are categorized into those of a type whose elongated insertion portion is rigid and those of a type whose elongated insertion portion is flexible.
On the other hand, in the case of endoscopes used in the industrial field, e.g., inspection of whether or not, e.g., damage or corrosion exists can be conducted by inserting a flexible elongated insertion portion into, e.g., a jet engine or a piping in a plant.
Furthermore, in the case of the medical endoscopes, various treatments and the like can be performed by introducing a treatment instrument to the inside of a body via a treatment instrument insertion channel provided in the insertion portion. On the other hand, in the case of the industrial endoscopes, various repairs and the like can be performed by introducing a tool to the inside of an engine through an insertion channel provided in the insertion portion.
In general, an endoscope including a flexible elongated insertion portion includes a bending portion on a distal end side of the insertion portion. The bending portion is configured to bend in a plurality of directions according to operations performed by a user via his/her hand. As described above, with an endoscope including a bending portion, the bending portion is bent to change a direction of observation via an observation optical system provided in a distal end portion of an insertion portion, enabling an inspection for a wide range to be performed.
Furthermore, in the case of an endoscope including a bending portion, when a distal end portion of an insertion portion reaches a flexed part provided in a conduit, the insertion portion can smoothly be inserted toward a deep portion of the conduit by properly bending the bending portion to direct the distal end portion toward the deep portion of the conduit.
A bendable bending portion is mainly configured by aligning a plurality of bending pieces in a longitudinal axis direction and pivotably joining the respective bending pieces so as to bend in, for example, two directions that are upward and downward directions, or four directions that are upward, downward, leftward and rightward directions, and is provided with a plurality of bending wires to respond to the bending directions.
Distal ends of the bending wires are fixed at respective predetermined positions in a distal end bending piece positioned on the distalmost end side from among the bending pieces included in the bending portion. On the other hand, proximal ends of the respective bending wires are fixed at respective predetermined positions in pulleys interlocked with, for example, bending knobs included in a bending operation device provided at an operation portion.
With such configuration, when a user performs an operation to rotate, for example, a bending knob for the upward direction, an upward bending wire from among four bending wires is pulled while a downward bending wire is loosened, whereby the bending portion bends upward.
In this case, the bending portion bends with a predetermined bending radius (also referred to as curvature) from a proximal end of the bending portion in a longitudinal axis direction of the insertion portion as a starting point. In other words, a bending portion configured by aligning a plurality of bending pieces is set to bend with a predetermined bending radius from the proximal end side of the bending portion as a starting point.
Japanese Patent Application Laid-Open Publication No. 2002-345742 discloses an endoscope of a type in which flexibility of a flexible tube portion is adjusted by change in bending stiffness of a coil, the endoscope being a flexibility-variable endoscope that provides enhanced operability and durability of a flexibility adjustment mechanism. The flexibility-variable endoscope includes a wire operation mechanism, which is illustrated in FIG. 2 in Japanese Patent Application Laid-Open Publication No. 2002-345742. The wire operation mechanism, a coil is provided in a flexible tube portion substantially concentrically with the flexible tube portion, a plurality of coil pull wires engaged with the coil are provided at different positions in a circumferential direction of the coil and the plurality of coil pull wires are pulled or loosened to expand/contract the coil. In the flexibility-variable endoscope, flexibility adjustment knobs are operated to pull the coil pull wires to contract the coil, enabling the flexible tube portion to be adjusted from a state in which the flexible tube portion easily bends (soft) to a state in which the flexible tube portion is hard to bend (hard).